aboutsummaryrefslogtreecommitdiff
path: root/include/drm/drm_modeset_lock.h
blob: 4fc9a43ac45a8f3c61b5542ae423747adb21056a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
/*
 * Copyright (C) 2014 Red Hat
 * Author: Rob Clark <robdclark@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef DRM_MODESET_LOCK_H_
#define DRM_MODESET_LOCK_H_

#include <linux/ww_mutex.h>

struct drm_modeset_lock;

/**
 * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx)
 * @ww_ctx: base acquire ctx
 * @contended: used internally for -EDEADLK handling
 * @locked: list of held locks
 * @trylock_only: trylock mode used in atomic contexts/panic notifiers
 * @interruptible: whether interruptible locking should be used.
 *
 * Each thread competing for a set of locks must use one acquire
 * ctx.  And if any lock fxn returns -EDEADLK, it must backoff and
 * retry.
 */
struct drm_modeset_acquire_ctx {

	struct ww_acquire_ctx ww_ctx;

	/*
	 * Contended lock: if a lock is contended you should only call
	 * drm_modeset_backoff() which drops locks and slow-locks the
	 * contended lock.
	 */
	struct drm_modeset_lock *contended;

	/*
	 * list of held locks (drm_modeset_lock)
	 */
	struct list_head locked;

	/*
	 * Trylock mode, use only for panic handlers!
	 */
	bool trylock_only;

	/* Perform interruptible waits on this context. */
	bool interruptible;
};

/**
 * struct drm_modeset_lock - used for locking modeset resources.
 * @mutex: resource locking
 * @head: used to hold its place on &drm_atomi_state.locked list when
 *    part of an atomic update
 *
 * Used for locking CRTCs and other modeset resources.
 */
struct drm_modeset_lock {
	/*
	 * modeset lock
	 */
	struct ww_mutex mutex;

	/*
	 * Resources that are locked as part of an atomic update are added
	 * to a list (so we know what to unlock at the end).
	 */
	struct list_head head;
};

#define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)

void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
		uint32_t flags);
void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx);
void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx);
int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);

void drm_modeset_lock_init(struct drm_modeset_lock *lock);

/**
 * drm_modeset_lock_fini - cleanup lock
 * @lock: lock to cleanup
 */
static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock)
{
	WARN_ON(!list_empty(&lock->head));
}

/**
 * drm_modeset_is_locked - equivalent to mutex_is_locked()
 * @lock: lock to check
 */
static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock)
{
	return ww_mutex_is_locked(&lock->mutex);
}

/**
 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held()
 * @lock: lock to check
 */
static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock)
{
	lockdep_assert_held(&lock->mutex.base);
}

int drm_modeset_lock(struct drm_modeset_lock *lock,
		struct drm_modeset_acquire_ctx *ctx);
int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
void drm_modeset_unlock(struct drm_modeset_lock *lock);

struct drm_device;
struct drm_crtc;
struct drm_plane;

void drm_modeset_lock_all(struct drm_device *dev);
void drm_modeset_unlock_all(struct drm_device *dev);
void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);

int drm_modeset_lock_all_ctx(struct drm_device *dev,
			     struct drm_modeset_acquire_ctx *ctx);

/**
 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks
 * @dev: drm device
 * @ctx: local modeset acquire context, will be dereferenced
 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init()
 * @ret: local ret/err/etc variable to track error status
 *
 * Use these macros to simplify grabbing all modeset locks using a local
 * context. This has the advantage of reducing boilerplate, but also properly
 * checking return values where appropriate.
 *
 * Any code run between BEGIN and END will be holding the modeset locks.
 *
 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and
 * forth between the labels on deadlock and error conditions.
 *
 * Drivers can acquire additional modeset locks. If any lock acquisition
 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with
 * the @ret parameter containing the return value of drm_modeset_lock().
 *
 * Returns:
 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN()
 * is 0, so no error checking is necessary
 */
#define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret)		\
	drm_modeset_acquire_init(&ctx, flags);				\
modeset_lock_retry:							\
	ret = drm_modeset_lock_all_ctx(dev, &ctx);			\
	if (ret)							\
		goto modeset_lock_fail;

/**
 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks
 * @ctx: local modeset acquire context, will be dereferenced
 * @ret: local ret/err/etc variable to track error status
 *
 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN
 * if ret is -EDEADLK.
 *
 * It's important that you use the same ret variable for begin and end so
 * deadlock conditions are properly handled.
 *
 * Returns:
 * ret will be untouched unless it is -EDEADLK on entry. That means that if you
 * successfully acquire the locks, ret will be whatever your code sets it to. If
 * there is a deadlock or other failure with acquire or backoff, ret will be set
 * to that failure. In both of these cases the code between BEGIN/END will not
 * be run, so the failure will reflect the inability to grab the locks.
 */
#define DRM_MODESET_LOCK_ALL_END(ctx, ret)				\
modeset_lock_fail:							\
	if (ret == -EDEADLK) {						\
		ret = drm_modeset_backoff(&ctx);			\
		if (!ret)						\
			goto modeset_lock_retry;			\
	}								\
	drm_modeset_drop_locks(&ctx);					\
	drm_modeset_acquire_fini(&ctx);

#endif /* DRM_MODESET_LOCK_H_ */